Embryonal stem (ES) cells and lineage- or tissue-specific stem cells are important models in biomedical studies, but the availability and accessibility of research materials in this rapidly advancing field often become limiting. These restrictions can be addressed by a central, internationally recognized Stem Cell Resource devoted to acquisition and distribution of cells, reagents and information on nonhuman ES cells and postnatally derived stem cells from a variety of species. ATCC is the oldest, largest and most experienced organization engaging in this type of endeavor. Mechanisms for efficient and cost-effective accessioning, characterization, expansion, preservation and distribution of biomaterials and information are firmly in place and highly utilized daily. To a large degree these procedures were developed at ATCC out of necessity, providing an atmosphere fostering continued experimentation and improvement. In addition, several ATCC scientists are pursuing research relevant to stem cell biology, providing a critical research orientation to the Resource. We propose to accession, characterize, expand, preserve and distribute nonhuman ES cells, as well as postnatally derived stem cells from a variety of strains and species. Through a consortium arrangement under the direction of Dr. Barbara Knowles at The Jackson Laboratories, germline competency of murine ES cells will be confirmed in a quantitative manner prior to distribution, - We will also carry out Resource-related research, in partnership with Dr. James Thomson, Univ. of Wisconsin, to extensively characterize stem cells with regard to biological properties and utility of molecular tools used in stem cell research. We will standardize and opting methodology and develop new reagents in an attempt to make procedures and reagents broadly applicable across a range of species and strains. We will also establish interactive, web-based mechanisms to distribute information and technology as well as materials, and serve as a centralized source for information exchange and rapid dissemination of advances in this extremely active field.